1. Field of the Invention
The present invention relates generally to a circular blade unit for cutting sheet material and, more particularly, to a circular blade unit which is adapted to be used with a template for a guided cutting system to cut sheet material, such as in an operation for cropping photographs.
2. Related Prior Art
In order to provide an attractive presentation of photographs in a scrapbook, the photographs are often cut or cropped, cutting away a peripheral portion of the photograph and leaving a central main subject portion of the photograph. Cropping of photographs provides an attractive border area for the photograph wherein the border area may be cut with a blade having a non-linear edge, such as a wavy or deckled edge.
Various devices have been proposed to facilitate the cropping operation including special scissors having wavy or deckled edges, and guided cutters such as the one disclosed in U.S. Pat. No. 701,828 to Arnold which incorporates a guide plate for guiding an arm movably supported on the plate to direct a cutting blade in a desired pattern for cutting sheet material. Other known guided cutting devices, such as for cutting circles or ovals, in a sheet of material include those incorporating a so called xe2x80x9cScottish yokexe2x80x9d mechanism which utilizes a base member supporting a pivoted arm and including two transversely oriented axes for guiding the arm in a controlled elliptical path. Typical examples of such devices are shown in U.S. Pat. No. 5,233,748 (Logan et al.) and U.S. Pat. No. 5,555,631 (Houston).
U.S. Pat. No. 3,456,346 (Snyder) discloses a circle cutter and protective cover in which the top of the cutter provides a handle for facilitating use of the cutter, and a removable cover is provided for protecting the bottom of the cutter from contact when not in use.
While known cutting devices provide the desired results of accurately following a desired shape, such devices are often complex and require assembly of several parts, and also are generally not well adapted to convenient and compact storage and transportation, a desirable attribute for equipment used by those involved in scrapbooking.
Accordingly, there is a need for an apparatus which facilitates cutting of sheet material and which requires a minimum of parts with accompanying reduced cost. In addition, there is a need for such an apparatus wherein a cutter is provided having means for protecting a user from contact with a cutting portion of the cutter when it is not in use.
In accordance with the present invention, a blade unit including a blade cartridge is provided for cutting sheet material. The blade unit includes a base member having opposing side portions and a bottom edge extending between the side portions. A blade is supported on the base member and includes an exposed portion extending past the bottom edge of the base member whereby the exposed portion of the blade is positioned to engage and cut material.
A cover member is provided for engagement with the base member, and the cover member includes wall portions defining a cavity for receiving the side portions of the base member therein. The wall portions of the cover member include opposing interior wall surfaces, and first and second detent members are provided on the opposing side portions of the base member and opposing interior wall surfaces of the cover member for cooperating with each other to hold the cover member in position on the base member.
The base member is positionable in engagement with the cover member in first and second positions, the first position comprising the first detent members located in engagement with the second detent members and the exposed portion of the blade located extending away from the cavity of the cover member. In the second position, the first and second detent members are located in engagement with each other with the exposed portion of the blade located extending into the cavity of the cover member.
In a further aspect of the invention, the blade comprises a circular blade supported for rotation on a pin extending through an aperture defined in the base member. In addition, the base member includes a substantially circular upper edge located adjacent the peripheral edge of the blade, and a guard flange is provided extending around the circular edge for preventing contact with the edge of the blade.
In another aspect of the invention, the bottom edge of the base member is provided with an elongated guide structure for engagement within a slot of a template to guide the blade unit along a desired cutting path.